Per diem and detention invoices, assembled into a dispute file your team can review and send.

A per diem or detention invoice names a container and a run of days. Someone in dispatch or billing pulls the outgate and ingate receipts, looks for the appointment or the turn-away, finds the agreement or tariff the bill rests on, works out the free time, and then decides whether to dispute, pay or let it go.

For the test, AI reads copies of those papers and drafts one dispute file per invoice: the fields the invoice carries and the ones it lacks, the container and free-time dates as billed, the gate transactions and appointment records that line up with those dates, the tariff or agreement named, the clock that applies, and each item that doesn't match. It takes no side. Your reviewer holds every file against what your team found and sent at the time.

The invoice has a required shape. Under 46 CFR 541.6, a demurrage or detention invoice from an ocean common carrier, marine terminal operator or NVOCC has to show the bill of lading and container numbers, the port of discharge on imports, and why you are the proper party to bill. It also has to show the invoice and due dates, the free time with its start and end dates, the container availability date on imports or the earliest return date on exports, the specific days charged, the tariff rule, terminal schedule or contract section behind the rate, a contact, and the windows for asking for relief. Section 541.5 says leaving out a required item ends the obligation to pay that charge. The draft goes down that list and names what is absent.

Two clocks can run on one container. Part 541 gives a billing party 30 calendar days from the date a charge was last incurred to issue the invoice, at least 30 from issuance for you to request mitigation, refund or waiver, and 30 from your request to try to resolve it. The UIIA, in its edition effective June 18, 2026, counts differently: section E.6.c gives a provider 60 calendar days from the equipment's return, after which its right to collect is lost. Unless the addendum sets its own process, section H gives a carrier 30 calendar days to dispute or lose the right, a provider 30 to answer or lose the charge, and the carrier 14 more after that answer to pay or go to binding arbitration. The draft names the clock it used and counts the days against it.

One section of the federal rule is gone. The FMC's 2024 rule included 46 CFR 541.4, on which parties could properly be invoiced. On September 23, 2025, the D.C. Circuit set it aside, faulting its blanket bar on billing motor carriers even when in direct contract with the billing party. The FMC removed it in a rule published December 29, 2025 and said the other provisions remain in effect. A dispute template that still leans on 541.4 is out of date, so the draft records only what the invoice says about why you were billed.

The proof has to be about this box on this day. A May 2015 UIIA panel decided a port congestion claim for the provider except on dates the carrier could show it was refused, and named what counts: rejection slips, correspondence with the provider, or dispatch messages from that day. Trade press on congestion didn't describe the facility at issue. A 2019 panel ruled against a carrier whose papers lacked unit-specific examples of empties it couldn't return on a one-way transaction. In January 2026, a panel sided with a carrier when the provider offered nothing beyond the invoice, though section E.6.e calls for evidence reasonably necessary to support it. The FMC's charge complaint guidance names truckers among those who may file and lists screen captures of denied return appointments and gate closures, and 46 CFR 545.5 says detention when empties can't be returned is likely to be found unreasonable absent extenuating circumstances. The draft ties each receipt, slip and message to a container and a date, and lists the dates with nothing behind them.

Small words and single days decide a lot. The UIIA treats a charge as per diem whether it's called that, detention or something else. A provider changing a return location owes you email by 4 p.m. local time the business day before, or one extra business day if the late notice held up the return. A 2018 panel settled a Memorial Day charge at a rail ramp on the addendum's wording alone. California's Business and Professions Code section 22928 bars these charges, at the terminals it covers, for the day or days when, among other cases, a truck gate is closed in posted hours, a diversion came without 48 hours' notice, or you document that no appointment was open in its shift windows. Your reviewer checks the wording, the version and the days. Nothing here is legal advice.

After your reviewer's yes, new invoices get the same file for about 30 days.

A dispatcher or billing person reads every file and decides whether to dispute, pay or let it go, and any dispute leaves from your office under your name.

A further job, if you want one, gets its own decision and its own price.